Could not fully normalize <T as Trait>::Assoc

[ivan770]

Code

I'm not sure about the exact part of code, that leads to ICE.
To reproduce issue, run clippy with unstable-options
https://github.com/ivan770/spartan/tree/fade05f7896c2ecd8413bf20273c4236a7faeb78

Meta

• cargo clippy -V: clippy 0.0.212 (fde6927 2021-01-02)
• rustc -Vv:

  rustc 1.51.0-nightly (fde692739 2021-01-02)
  binary: rustc
  commit-hash: fde692739576089729885b7f79aa2232cb9778c5
  commit-date: 2021-01-02
  host: x86_64-unknown-linux-gnu
  release: 1.51.0-nightly
  

Error output

error: internal compiler error: compiler/rustc_traits/src/normalize_erasing_regions.rs:43:32: could not fully normalize `<M as core::payload::identifiable::Identifiable>::Id`

thread 'rustc' panicked at 'Box<Any>', compiler/rustc_errors/src/lib.rs:958:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

note: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust-clippy/issues/new

note: Clippy version: clippy 0.0.212 (fde6927 2021-01-02)

query stack during panic:
#0 [normalize_generic_arg_after_erasing_regions] normalizing `<M as core::payload::identifiable::Identifiable>::Id`
#1 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to previous error

Backtrace

stack backtrace:
 0: std::panicking::begin_panic
 1: rustc_errors::HandlerInner::bug
 2: rustc_errors::Handler::bug
 3: rustc_middle::ty::context::tls::with_opt
 4: rustc_middle::util::bug::opt_span_bug_fmt
 5: rustc_middle::util::bug::bug_fmt
 6: rustc_infer::infer::InferCtxtBuilder::enter
 7: rustc_traits::normalize_erasing_regions::normalize_generic_arg_after_erasing_regions
 8: rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps
 9: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
10: rustc_data_structures::stack::ensure_sufficient_stack
11: rustc_query_system::query::plumbing::get_query_impl
12: rustc_middle::ty::normalize_erasing_regions::<impl rustc_middle::ty::context::TyCtxt>::normalize_erasing_regions
13: <rustc_middle::ty::layout::LayoutCx<rustc_middle::ty::context::TyCtxt> as rustc_target::abi::LayoutOf>::layout_of
14: <rustc_lint::context::LateContext as rustc_target::abi::LayoutOf>::layout_of
15: <clippy_lints::zero_sized_map_values::ZeroSizedMapValues as rustc_lint::passes::LateLintPass>::check_ty
16: <rustc_lint::late::LateLintPassObjects as rustc_lint::passes::LateLintPass>::check_ty
17: <rustc_lint::late::LateContextAndPass<T> as rustc_hir::intravisit::Visitor>::visit_ty
18: rustc_hir::intravisit::walk_item
19: rustc_hir::intravisit::Visitor::visit_nested_item
20: rustc_hir::intravisit::walk_mod
21: <rustc_lint::late::LateContextAndPass<T> as rustc_hir::intravisit::Visitor>::visit_mod
22: rustc_hir::intravisit::walk_item
23: rustc_hir::intravisit::Visitor::visit_nested_item
24: rustc_hir::intravisit::walk_mod
25: <rustc_lint::late::LateContextAndPass<T> as rustc_hir::intravisit::Visitor>::visit_mod
26: rustc_hir::intravisit::walk_item
27: rustc_hir::intravisit::Visitor::visit_nested_item
28: rustc_hir::intravisit::walk_mod
29: <rustc_lint::late::LateContextAndPass<T> as rustc_hir::intravisit::Visitor>::visit_mod
30: rustc_hir::intravisit::walk_item
31: rustc_hir::intravisit::Visitor::visit_nested_item
32: rustc_hir::intravisit::walk_mod
33: <rustc_lint::late::LateContextAndPass<T> as rustc_hir::intravisit::Visitor>::visit_mod
34: rustc_hir::intravisit::walk_crate
35: rustc_lint::late::late_lint_pass_crate
36: rustc_session::utils::<impl rustc_session::session::Session>::time
37: <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once
38: rustc_session::utils::<impl rustc_session::session::Session>::time
39: rustc_interface::passes::analysis
40: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::analysis>::compute
41: rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps
42: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
43: rustc_data_structures::stack::ensure_sufficient_stack
44: rustc_query_system::query::plumbing::get_query_impl
45: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter
46: rustc_span::with_source_map
47: rustc_interface::interface::create_compiler_and_run
48: rustc_span::with_session_globals

[giraffate]

Thanks for your report!

I guess it might be related with rust-lang/rust#80045.

[rail-rain]

I have extracted a minimal repro from the original crate:

use std::collections::BTreeMap;
pub trait Identifiable {
    type Id;
}

type _Tree<M> = BTreeMap<(), <M as Identifiable>::Id>;

Playground

This means the underlying cause is that, in zero_sized_map_values, Clippy indirectly calls normalize_erasing_regions; which triggers the panic because that cannot normalize <M as Identifiable>::Id there. This is an expected behaviour since its document states "This is appropriate to use only after type-check: it assumes that normalization will succeed, for example.".

[tdyas]

Just wanted to flag that #6840 is an ICE in v1.50.0 related to normalize_generic_arg_after_erasing_regions that is not fixed by the PR linked to this issue.